168 GEOLOGY OF THE THIRD DISTRICT. 



24. GENESEE SLATE. 



Black Shale and Slate, and Upper Black Slate of the Reports. 



43. 



No. I. liOdi oiWeaU (O. lodeniis). No. 3. Spatnlate lingula (L. spatul&U). 



2, FoiUHribbed orthis (O. quadracotuta). 4. Concentric lingula (L. concentrica). 



The Genesee slate is an argillaceous fissile mass, which with great propriety might be 

 termed, according to English local geological phraseology, a mud rock. It is a thick rock 

 towards Cayuga lake, rising upon the Tully limestone for about one hundred feet at its maxi- 

 mum. Its color is black, and very uniform ; and so is its structure, being more or less slaty, 

 and somewhat hard and brittle ; but like all the upper fine-grained argillaceous rocks of the 

 district, though its edges resist the weather, its surface, when exposed, falls into pieces, and 

 readily decays. The joints in the rock are two in number, usually well defined, and their 

 direction nearly at right angles to each other ; thus, near Ludlowville, one is N. 8° W., and 

 the other E. 12° N. 



This rock contains but few fossils ; those only which are figured in the wood-cut having 

 been seen in it in the district, with the exception of a well defined impression of a leaf about 

 six inches long, broken at both ends, and a fifth of an inch wide, resembling a linear leaf 

 of grass or sea-weed, the surface smooth. The fossils of the wood-cut were not generally' 

 diffused, but quite numerous in a few localities on Cayuga lake ; and the best localities for 

 obtaining them are the ravines near Ogden's ferry, towards the upper part of the mass. 



It contains a few septaria, well formed and characterized, appearing either in one or two 

 ranges, far removed from each other ; the septaria in each range being also wide apart. The 

 fissures or septa are often lined with lamellar sulphate of strontian, carbonate of lime, and 

 a few quartz crystals. In one of the septaria from the ravine at Ogden's ferry on Cayuga 

 lake, there was a liquid substance of the color of phosphate of iron or prussian blue, and an- 

 other substance resembling spermaceti before the oil is fully pressed out. It was composed 

 of small scales, hard and yellowish white, and was in small irregular formed masses of the 

 size of a pea, with an appearance of having been melted. The blue liquid was entirely lost ; 

 the white substance, though carefully packed up in the cavity of the specimen, disappeared, 

 for nothing of it was found when unpacked. These same substances have been noticed by 



